AcoustiPack Noise Damping Kit

Cases|Damping
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February 11, 2003 -- by Mike Chin

Product AcoustiPack™ - Deluxe / Standard
Manufacturer Acousti Products
Selling Price Deluxe: UK£39 - US$90 / Standard: UK£21- US$54 -- Based on current QuietPC online catalogs. Prices outside UK greatly affected by high shipping weight / cost of products. Should drop as sea shipping is utilized.
Other Products considered

- Pax.mate by Akasa <~US$20)
- ProStudio by CoolerMaster <~US$20)
- Wispermat by Muffled Computing - US$20 online

Acoustic damping materials are virtually ubiquitous in the modern world. Fiberglass batting, foam, and all manner of specialized materials are used in an incredible range of applications to combat and control noise. In computers, however, it is not yet common. One place many SPCR readers may have seen it is beneath the metal protective cover of the Seagate Barracuda IV hard drive: a bit of blue foam is visible there. This foam helps to keep the Barracuda relatively free of high frequency whine. The fact that this quietest of all hard drives uses damping materials is probably significant. As far as I am aware, no other hard drives incorporate acoustic damping materials.

In my own systems, some damping materials are used -- things like heavy carpet underlay and recycled foam from packing materials -- but until now, I have never tried any of the aftermarket damping materials sold specifically for computer cases. There is little question that acoustic damping can help reduce noise.

The main question is,

How much money, time, and effort is required with acoustic damping materials to obtain what level of noise reduction in a PC?

Many PC silencers are of the opinion that using the quietest components and reducing the noise of components at their source makes damping materials unnecessary. This was generally my point of view, too. My perspective has been changed with exposure to the product under review.

This article began originally as a comparative review of four brands of damping materials marketed for use in a PC case. All share the common feature of being backed with adhesive on one side so that it is relatively simple to apply. They're shown in the photo below (clockwise from top left):

Why this article turned into a review of just the one product will become clear as you read on.

TEST METHODOLOGY / PLATFORM

After a great deal of research into the question of how to analyze the effectiveness of these damping materials, I came to the unavoidable conclusion that there is only one practical way:

Apply the damping to a case as recommended by the manufacturer and compare it to an unmodified case of the same type, the same model, with the same noise sources (computer components) in it.

This conclusion took a long time to reach, mainly because it was the one I wanted most to avoid. Why was I so loathe to use this methodology?

Applying the damping looked like a mountain of tedious work, especially without at least one pair of matching cases. My hands were going to take a beating...

Fortunately, Antec came to the rescue by generously sponsoring another Sonata case, this time a pre-production black one to match the earlier beige sample used for the review conducted some weeks ago. This seemed a reasonable case to use as a test platform, as the Sonata is designed specifically as a reduced-noise case. Thank you Antec!

Still this meant applying four and removing at least two sets of the damping materials. Ideally, what I wanted was five identical cases. (Good thing I didn't get them! As you know the review only focuses on one product.)

NOISE CHALLENGES

Before getting into the product details, it seems worthwhile to consider the challenge noise damping materials face in a PC. Here are some basic observations:

1. The main goal is to reduce noise -- all noise. In a typical PC, there are high-pitched whirring noises from hard drives and small high speed fans, the mid/high frequency noise of fan turbulence, the lower frequency rumbling and clacking seek noise from hard drives. While we tend to identify the more annoying high frequency noises quickly, there are noises in every frequency band.

  • The damping materials must be effective not in a narrow or limited bandwidth but across the entire audible frequency range.
2. The case is made of thin metal panels and plastics, which do not block, contain or dampen the noise inside well. The metal chassis and panels often vibrate, sometimes subtly, sometimes obviously, adding their own noise to the mix. This noise is usually lower in frequency, but their sympathetic vibrations add to the whole mix of noise.
  • The damping materials must reduce or eliminate sympathetic panel resonances that contribute to the noise, and increase the noise blocking/containing capability of the case panels.

3. The case has air vents that allow noise to escape directly and easily. Sound becomes more directional higher in frequency, becoming more like narrow beams of light rather than waves from a splash in a pool (the behavior at lower frequencies). So in theory, it should not be that hard to minimize high pitched whining or whistling by eliminating direct paths to the ears. In practise, as most PC silencers know, high pitched noise is not easily eliminated by baffles alone, most likely because there are many hard and reflective surfaces that noises bounce off to find their way out the openings, regardless of frequency.

  • The damping materials must reduce the noise and reflections within the case by absorbing it as much as possible. Coverage of as much internal surface area as possible is likely desirable.

4. Other desirable qualities.

  • Nonflammable -- Acoustical or soundproofing foam is most often made from polyester, polyurethane, or some other poly-something or other, all of which have a tendency to be at least somewhat flammable.
  • Doesn't smell -- Nasty smells have been reported to emanate from damping materials, especially as the computer case heats up. It is not clear whether this smell is accompanied by any toxic outgassing or is simply unpleasant.

PRODUCT COMPARISON

How do the contenders fare on the points under NOISE CHALLENGES?

Product
Mass (grams)
Thickness (mm)
Density
Size (cm)
Paxmate
<200
3.2
very low
2 - 40 x 34, 2 - 40 x 17
Pro-Studio
<200
12.7, 28
very low
2 - 30 x 24
Whispermat 1/2"
~550
12.7
high
1 - 25 x 25
Whispermat 1"
~700
25.4
high
1 - 25 x 25
AcoustiPack™ Sandard
3400
12.5
high
3 - 49.5 x 39.5
AcoustiPack™ Deluxe
4600
2.8, 12.5, 19
high / very high
5 - 49.5 x 39.5 (more)

The Akasa Paxmate is far too light, way too thin and has too low a density to meet any of the criteria set above. Its total area coverage is the only way that it passes -- just barely, but it is a minor 1 out of 4. It is simply not worthy of a serious look. It also smells terrible, although one user mentioned it seemed to go away after a few days. It is unlikely that applying this product could have any significant impact on the noise of any PC in any case. Anyone with the least bit of understanding of acoustic damping will come to that conclusion in a 30-second examination. Not recommended.

The Cooler Master Pro-Studio comes in a really nice lime green translucent plastic case with handles and snap locks. It's the nicest part about this kit. It is too light, too low in density, and covers way too little surface area to have any affect to noise in a PC. If 4 or 5 kits were purchased and their entire contents applied to the interior of a PC case, there would probably be a small decrease in high frequency noise. Not recommended.

As the above profile of the 1" Wispermat by Muffled Computing shows, this is a composite of 3 materials. The thin grey strip in the center is a dense vinyl layer. The acoustic foam on either side of the vinyl layer is considerably less dense. The thicker outer layers seems stiffer and more coarse, while the inner layer closest to the adhesive seems both softer and finer. Its weight and density is very close to that of the Acousti Products Acoustic Composite sheet (see below). Wispermat is thick enough, dense enough, and heavy enough; alas only one 1/2" sheet and a 1" sheet were provided. Not nearly enough to conduct a full review. They were excluded from this roundup only for that reason, and will be the subject of a review in the near future.

ACOUSTIPACK™ DETAILS

AcoustiPack™ Deluxe: 4.6 kg (over 10 albs) of 4 different types materials

Acousti Products, based in the UK, are relatively new to the market. They offer two kits, a standard and a deluxe version, the latter offering more materials, and more types of materials for a larger case. The variety of materials in the deluxe kit indicates an approach that is considerably better thought out and more sophisticated than others. Both kits easily meet all the above criteria.

Referring to the photo above, starting with the materials on top and moving down, the Deluxe AcoustiPack™ contains...

  • 1 precut rectangular block of Acoustic Foam for spare 3½ inch drive bays.
  • 2 precut rectangular blocks of Acoustic Foam for spare 5¼ inch drive bays.
  • 1 Acoustic Foam sheet featuring the AcoustiContour™ anechoic surface
  • 2 Acoustic Composite sheets - 12.5mm thickness (2.5mm Acoustic Barrier Mass and 10mm Acoustic Foam)
  • 2 Acoustic Barrier Mass sheets - 2.5mm thickness

Each of the 5 sheets measures a substantial 495 x 395mm (19.4" x 15.5"), which is large enough to cover the entire side cover of almost any tower case. The total weight of the package is substantial, at 4.6 kg (10 lbs).

The Standard AcoustiPack™ has 3 Acoustic Composite sheets (same size as in the Deluxe kit).

Acousti Products' web site has extensive details about these various materials. It provides the most comprehensive information of all the PC damping materials referred to above. It even includes this graph showing lab measurements of the materials' damping qualities. All this is impressive, as it suggests a carefully studied approach to development, rather than the typical marketing-driven, me-too approach.

Acoustic Foam -- AP use a semi-open cell, polyurethane foam. This is approx. 65 kg/m³ - unusually dense compared to alternative noise-reduction foams. The advantages claimed for high density foam:

  • Improves sound absorption efficiency at lower frequencies (sub-1KHz) - said to be critical
  • Helps to maintain a low flammability performance, and
  • Withstands being manufactured into thin 'low-reflection' layers for dual-layer composites

"The acoustic foam is certified UL94, ISO 3582, FMVSS 302 and DIN 4102 for low flammability, and can be operated normally within the temperature range -40°C to +120°C."

Acoustic Barrier Mass -- This quote is from AP:

"Manufactured from a flexible polymeric material incorporating additional mineral fillers to increase mechanical strength, durability and fire resistance. The material is not bitumen-based, and does not give off undesirable odors when warm. This material is very dense at approx. 2000 kg/m³. It is designed to add mass to computer casing, for example, sheet aluminium, steel, alloys and non-glossy plastic surfaces. The material mass acts as an acoustic absorption barrier, significantly reducing noise transmission and reducing any natural resonance frequencies." It is considerably more effective at sub-1000Hz frequencies than the acoustic foam.

"The acoustic barrier mass is certified to ISO 9772, DIN 75200, ISO 3795 and FMVSS 302 for low flammability, and can be operated normally within the temperature range -25°C to +120°C."

They recommend combining the Barrier Mass with the Acoustic Foam whenever possible -- for example, on the main left side cover. This ensures the best broadband noise reduction. Their Acoustic Composite sheet, which is not described in detail, is a composite of these two materials. The photo below shows the profile of the composite sheet; the thin lighter gray layer is the heavy barrier mass:

Adhesives: Acousti Products use water-based, nonflammable adhesives. They say these are

"less odorous than solvent-based adhesives in some similar products... and can be operated normally within the temperature range -20°C to +150°C. If a mistake is made during the application of acoustic materials, our adhesive allows for the materials to be peeled off and then reapplied."

A Caution:

"Although the range of operating temperatures stated above are those published by the manufacturers of the raw materials - we strongly recommend that materials are not placed directly against hot components. This is to ensure that products are installed with optimal safety in mind and to help maintain hardware longevity. Always read the printed instructions with each product prior to installation."



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